Being the Demon Emperor is really, really boring.
Every day Mianmian still attended court, reviewed memorials, and punished erring demons.
Since she was illiterate, the memorials were all read to her by Yunshang, and then she told Yunshang what to write. Yunshang then wanted her to learn to read.
Mianmian originally didn't want to learn to read, but her parents agreed to it and insisted she go, so with no choice, she could only agree.
Su Ji was also learning, but he was learning more than her.
After attending lessons alone for a long time and finding it boring, Mianmian came up with the great idea to have the children of the ministers also come to the palace to study with her.
These children had to be about her age, none older than her.
So, according to Mianmian's requirements, Yunshang chose eleven little study buddies for her.